1. Field of the Invention
The present invention relates to a magnetic read/write apparatus, and more particularly to a technique effective in reducing the occurrence of erasure of neighboring tracks and increasing the track density.
2. Description of Related Art
A magnetic read/write apparatus writes data onto a plurality of tracks as magnetized patterns. When a write operation is performed, a head seeks a track specified by servo information written in a servo sector, and after the head is positioned in place, data is written onto a surface of the medium.
At that time, whether the head has been positioned in place is determined based on the amount of displacement of the head from the center of the target track used as a reference. If the amount of displacement is within a predetermined threshold value, the write operation is carried out. If it is larger than the threshold value, the write operation is inhibited. This threshold value is referred to as a write inhibit slice.
The write inhibit slice must be set to an optimum value in terms of protection of the data on the neighboring tracks and the data transfer rate in the write operation. Conventionally, the write inhibit slice is generally set to a fixed value for each drive model; no more than one write inhibit slice value is used within a same drive.
However, the value of the write inhibit slice can be properly set and controlled so as to avoid fatal problems such as direct erasure of neighboring tracks while increasing the track density.
Conventionally, to accomplish the above object, the write inhibit slice may be set asymmetrical about the center of the track to prevent erasure of neighboring tracks due to the asymmetry of the shape of the erase band attributed to the skew angle of the head, as described in, for example, Japanese Patent Laid-Open No. 2000-173005. Further, the write inhibit slice may be set to different values depending on the recording radial position of each track on the disk to reduce variations in the frequency of write inhibit operations (frequency of occurrence of write faults) among the disk radial positions due to variations in the head alignment accuracy among the disk radial positions, as described in, for example, Japanese Patent Laid-Open No. 2002-92803. Still further, write position information on each sector may be stored such that when a read operation is performed, the read head can accurately trace the write positions (path) at which the data was written and thereby enhance the reliability of the read data, as described in, for example, Japanese Patent Laid-Open No. 2002-133802.
The methods described in the above Japanese Laid-Open Patent Publications were devised to solve the problems caused by increased track density. To further increase the track density, however, it is necessary to address, in addition to the above problems, the problem that as the number of write operations performed on a same sector increases, the data in its neighboring sectors (tracks) are gradually erased (erasure of neighboring tracks).
This phenomenon may occur when a high magnetic field is produced even though a write head for a narrow track width is used in order to provide a write magnetic field higher than that conventionally employed. At that time, the magnetic field leaks in the track width direction of the write head. This significant problem must be solved in order to further increase the track density.
Since the methods described in the above Japanese Laid-Open Patent Publications can hardly prevent occurrence of the above phenomenon, a new write control method must be devised to solve the problem.